Combines are large machines that harvest, thresh and clean grain in a field. A combine comprises a number of adjustable elements, like the size of openings in a threshing concave or in a separating grate, the speed of a cleaning shoe blower and the position of louvers in a sieve. The optimal working parameter of these elements depends on the crop type and properties and can change over time. The adjustment of these parameters is usually performed by the combine operator based upon instruction manuals or his experience or automatically based on values stored in a memory and recalled dependent on actual conditions by the operator. In the past, numerous sensors for sensing crop properties (like capacitive moisture sensors, cameras and near infrared spectrometers) have been proposed to evaluate crop properties on board of the combine to provide input for an automatic control of one or more of the working parameters. Another use of the sensors is to collect crop parameters for precision farming or documentation purposes, in particular in forage harvesters, combines and balers.
The presentation of the crop sample to the sensor is critical to obtain an appropriate sensor output. The prior art comprises among others sensors mounted directly to the outer wall of a cross auger in a cleaning system that delivers the cleaned grain to a clean grain elevator (U.S. Pat. No. 5,092,819 A1), in a bypass of the clean grain elevator or of the cross auger (U.S. Pat. No. 6,327,899 A1), or at the downstream end of an auger that receives crop through an opening in the wall of a crop acceleration blower of a forage harvester (DE 102 36 515 C1). Further, it was proposed to feed a part of the crop residues downstream a straw chopper to a comminuting device and then to a near infrared spectrometer (EP 2 119 339 A1). This arrangement is not suited for checking properties of grain, since it would destroy the kernels.
When grain is fed in a horizontal auger, like in the prior art cross augers, and the sensor looks into the interior of the auger tube, the problem arises that when the crop flow is relatively low, such that crop is only present at the bottom of the tube, no reliable sensing is possible due to lack of sufficient crop material in front of the sensor. A similar problem arises when the harvesting machine drives up or down a hill. Mounting the sensor at the bottom of the auger tube, such that it looks upward upon the crop, does not resolve this problem, since smaller particles of the crop collect at the bottom of the tube, while the grain collects above these smaller particles.
Thus, there is a need for a crop sample presentation system that provides a representative, realistic sample of the crop in front of a crop sensor.
It is an object of the present invention to provide a sample presentation system improved over the prior art.